On CNN, Jane Velez-Mitchell offered possible theories about the crime, saying, "With this situation, if you look at it and you say, 'What happened here?' Could he have had some kind of fixation on her? When it comes to these cases, it's usually only a handful of possibilities."

The 24-year-old victim had a Twitter page that reflected her optimistic look on life.

"Every day may not be good, but there's something good in every day," she had tweeted.

The crime sent shock waves through Danvers High School, a true picture of small-town America.

Ritzer lived with her parents and was working on her Masters' degree.

Her family said in a statement: "At this time we are mourning the tragic death of our amazing, beautiful daughter and sister. Everyone that knew and loved Colleen knew of her passion for teaching and how she mentored each and every one of her students."

Her students shared their grief online.

"Rest in peace Ms. Ritzer. You were an amazing person and will forever be a part of our community," wrote one student.

Another wrote: "You were the nicest person I know, life isn't fair."

There is no known motive for the crime. The suspect pleaded not guilty and is being held without bail.